


All Hail This Halloween

by TheNinjaMouse



Category: Undertale (Video Game)
Genre: F/M, M/M, tags to be added!
Language: English
Status: In-Progress
Published: 2020-11-01
Updated: 2020-10-31
Packaged: 2021-03-09 03:01:40
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,699
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27277672
Author URL: https://archiveofourown.org/users/TheNinjaMouse/pseuds/TheNinjaMouse
Summary: A collection of Halloween prompts and stand alone pieces! Tags to be added as needed
Relationships: W. D. Gaster/Grillby/Reader, W.D. Gaster/Reader, grillby/reader
Comments: 4
Kudos: 41





	1. Welcome now the spirits of Old Samhain Night

**Author's Note:**

> At Samhain the division between this world and the otherworld is at its thinnest, allowing spirits to pass through.

**Notes for the Chapter:**

> First of the requests! Some talk of the differences between the Halloween of today and the cultures celebrated by monsters at this time of year
> 
> Samhain (sow-win): celebrated from October 31 to November 1 to welcome in the harvest and usher in “the dark half of the year.”

The door to the bar slams open and W.D Gaster strides in much like the night wind outside; fierce, sudden and with the sort of intensity that made one’s spine shiver.

“Once again, humanity strikes with its modern, twisted views on a long time practice of honor and respect!”

He stops, taking in the sight in front of him. And what a sight it is. You’re currently hanging upside down with one foot tangled precariously in ropes and garlands stuck to the rafters of the high ceiling. There’s a pile of fake bats fallen tragically to the floor next to a tipped over ladder. You _might_ have ignored the warning not to use the top step and lost your balance. Luckily, the end of the rope had been draped over the ladder and somehow managed to wrap around your ankle. Hanging as you are, you’ve all but become part of the spooky décor. Grillby ignores Gaster, a little too preoccupied with making sure you don’t fall and break your neck.

Gaster blinks. “Goodness.”

“Indeed!” you say brightly as you spin around in a slow circle. “Don’t mind me, what is it the whole of humanity has done now?”

Gaster scowls and steps over the fallen ladder, headed straight for the bar. No doubt to fuel his indignant rage at whatever has his nerves set off tonight. He waves a hard sharply. “Oh, just turned an ancient practice into a night of mockery and scares as a thin excuse to sell cheap plastic toys and candy.”

“Capitalism strikes again.” Your face is now quite red thanks to the blood rushing into your head. Grillby, having had quite enough of your swinging precariously from the ceiling, simply sends a hot ball of flame into the taunt rope a few inches up from your foot. You yelp as the cord burns and then snaps, sending you straight into Grillby’s waiting arms. “Oh, thank you dear.”

“Let’s maybe let Gaster help with the ceiling decorations,” he says rather mildly. He plops you down on the surface of a table and goes to work on de-tangling the rope around your ankle. He’s trying to be gentle, but your ankle is already starting to swell and you wince.

“Oh, why _not_.” Gaster, quite morosely, slumps down on a barstool with a bottle of scotch stolen from behind the counter. “We shall _join_ the system, yet another den of candy and scary monsters for the humans to ogle at.”

You and Grillby share a glance. Foot free, you hop down, squawk as your sore ankle gives out a little, and make your way over to the sad skeleton currently leaning over the bar top in a weak attempt to grab a glass for his drink. “I honestly would have thought that Halloween was something you’d be pumped about.”

Gaster gives up trying to reach the glass and sighs. “I’m afraid that I was. But it would seem that your Halloween and my Samhain now have less in common than a rock and a gumball.” 

You blink, trying to take in that comparison, then shake your head. “What’s Samhain?” you ask, carefully pronouncing the unfamiliar word.

Gaster shifts a little, gesturing for you to sit down. Once you do, he reaches for your ankle, propping your foot on his knee. His cool bones on the swollen skin makes you hiss out a soft breath somewhere between pain and relief. “Samhain was one of the four great Celtic festivals that took place every year. It marked the time of year when the fires of our hearths would be set to rest, and livestock brought home. We lit new fires to stand against the dark and cold in the winter months. And it was during this time that the Souls of those passed on would skirt the boundaries of our world. Ancient spirits that came before the first monsters were born from the dust of fallen stars were said to dance among the living on that night when veils between worlds and boundaries between time grew thin. Though those spirits of a more…unsavory nature could steal away those with their guard down, taken away to the world of mists and darkness.”

“Celtic…so you’re Scottish too?”

“British actually.” Gaster grins, all teeth and cheeky glee. “You wouldn’t know it from my accent, would you?”

“Yeah, I don’t think your accent can be counted as anything remotely human.”

Grillby snorts quietly, having moved back behind the bar. He takes pity on Gaster, pouring him a glass of whiskey. Gaster nods his thanks, takes the drink, and continues. As he talks, he very gently massages your ankle, little sparks of green magic dancing from his fingertips. “Samhain actually started in Ireland and that was where my grandparents were born. So, we crossed the Muir Éireann a few times a year for the festivals. Many monsters in the highlands practiced it too, or at least versions of it.”

“It sounds a bit like All Hallows Eve.” That old practice you do know a little bit about. A night where early Christians believed that evil spirits roamed the earth and had kids disguise their faces to trick the spirits into thinking they were also of the ‘dearly departed’. Or something like that.

“Ah, they do share similarities.” Gaster’s magic has finished it’s work on your ankle, but he keeps a gentle hold on it. His hands, always so fidgety when he talks, have seemed to have settled on tapping out light patterns against your skin. “Humans had their own takes; ones that circulated around their own gods and used us monsters as the devils and spirits, once we were no longer in obvious sight among them. But our Samhaim! Oh Grillby, do you remember the one we had once were settled into the valley?”

Grillby, flickering with soft hues of gold and amber, smiles gently. A few sparks lift from his head. “I couldn’t walk more than few steps without someone trying to warm their hands on me. I was so confused and this one-” Grillby jabbed a finger lightly into Gaster’s chest. “This one thought it would be funny to act like he knew nothing about what was going on.” 

“You can hardly blame me Sparks. You’re too much fun to tease.”

There’s a warm and yet, slightly bittersweet feeling growing in your heart. It’s a familiar one. The history that Gaster and Grillby share spans over hundreds of years. All the way back to the war and the great crossing of monster kind over the sea in an attempt to escape the humans hunting them down. There’s a history between them and though you know much of it, there’s still a bond there that runs far deeper than the one you’ve built with them over such a short time.

“I still cannot believe you had me convinced that everyone had gone crazy from evil spirits!” Grillby, still washed with warm colors, has one hand on his hip as he playfully scowls at Gaster. “Said the only way to cure them was to light a bonfire in the center of town and dance around-Shore stop grinning at me like that.”

You’ll do no such thing! “Come on, you have to show me!”

He hums thoughtfully. "No." 

You pout. "Party pooper. G?" 

"Gladly, my dear." Gaster rises from his stool, misery of before gone in the light of suave playfulness. You accept his outstretched hand. The room is mostly clear, save for the fallen ladder and bats, which is easily pushed aside. He starts to hum, a shockingly deep sound for someone with no actual lungs. His feet tap a steady rhythm against the floor, all gangly bones and limbs and you do you best to follow his lead as he moves around in a circle. He leans in close, pseudo breath ghosting against you ear as he whispers, "Just make him jealous, he'll be out here in a flash." 

Oh you know. You grin. "What a shame we have no fire to dance around," you call loudly over to Grillby. 

He flicks a hand. A soft ball of flame bursts into life, floating about four feet from the ground. In the same motion, the lights around the bar go dim, so that Grillby and his fireball are the main sources of light, casting deep shadows throughout the bar. 

Gaster is humming again and then he starts to sing as he spins and leaps about. And to your surprise, the words are tinged with an Irish accent. Combined with his usual underlying Wingdings, you find yourself utterly entranced by how otherworldly his voice is. 

_"Light the sacred fires, hold your lover tight, welcome now the spirits of Old Samhain Night."_ His eyelights glow with his glee as the two of you dance around your tiny bonfire. From the bar, Grillby begins to tap out a beat on the bartop with his hands, a _rat-tat-a-tat_ beat that your feet automatically shift to follow.

 _"Let not your heart be heavy, let not your head be light."_ Gaster moves you out into a spin and back in, hand resting on your hip. _"Keep aware and quench you fears, on this Samhain night."_

It's a lovely song, made lovelier by Gaster's voice. You lose yourself in it and the dance, then before you know it, cool bone is replaced by heavenly warmth. Grillby moves with more grace than your gangly skeleton but perhaps with a little less freedom. You smile at him, the light of his fire reflecting in your eyes as you encourage him to follow you as you gently move back with a hand on his wrist. All the while, Gaster continues to sing, his hands clapping out beat that is a little softer thanks to the delicate nature of his bones. 

You gesture him closer and you find yourself nearly sandwiched between the two as he finishes, _"So hold your lover tight and walk though in a sweet dream through Old Samhain Night."_ He taps your nose, making your face crinkle up. _"Where things are never as they seem."_

You laugh a little breathlessly as you all part and the lights return to their normal level. "Perhaps there is something to this Samhain night of yours." 

Gaster nearly preens with smugness, causing Grillby to crackle and snort quietly. 

You lift your finger. "However! The month is just beginning. Let me show you what Halloween is like behind the flashy ads and staring humans. There's a lot to like." 

Gaster's sockets narrow slightly, considering. "Very well. What did you have in mind?" 

There's no effort to hide your utterly delighted grin as the beginning notes of 'This is Halloween' run through your head. "Oh I have some ideas." 


	2. Boo To You!

**Notes for the Chapter:**

> A LOT of y'all asked for a Haunted House thing which I wrote way back in the year of our Dog Lord Toby 2017 (oh lordy, I've been writing OoF stuff for nearly 4 years now)  
> So! I found it and revamped it a bit! Just a note that when this was written, it was still in the early stages of the Shorby relationship!

Getting Grillby to agree to take an early night from the bar is a feat all by itself. But the town is decked out in orange, blacks and reds, paper bats and skeletons adorn shop windows and today, on this particular Halloween, you’ve decided to finally muster up the courage to visit the self proclaimed ‘Nation’s Scariest House of Horrors’ after refusing to go for years. 

The problem is, you don’t have quite enough courage to go by yourself. And your usual group of people you would ask are either too chicken to go, or would honestly probably make the experience ten times worse. And then there was Undyne, who was absolutely thrilled at the idea of going, but she had already planned a romantic/spooky movie date night with Alphys who gave you a firm no on going. You did ask Sans, as much as you get the feeling that he would just prank you to add to the spooks but he said he was working. Probably got a gig somewhere as a spooky scary skeleton. He was actually the one who suggested that you ask Grillby. You have to admit the idea is appealing. Not only because of his calm demeanor and natural light to help stave off the creepy darkness a bit but you can’t imagine he’ll complain about you holding onto his arm for courage if you have to.

It had taken a bit of begging and a lot of persistence, but he had finally agreed to close up an hour early. You head to the bar just a few minutes before 11, passing a fair amount of patrons in varying degrees of costumes and drunkenness as you do. Grillby himself steps outside just as you arrive. His flames brighten in greeting, though when you frown at him, he dims slightly.

“Where’s your costume?“ you demand, hands on your hips. 

He looks at your outfit, a mismatched wizard’s outfit and a button that reads ‘Sizzle It Up With Taako’ and glances down at his usual bartending look. “Is that required?” 

“Absolutely. Fortunately for you-” You grin and dig into your bag, pulling out a black cape. “I came prepared.” You motion for him to bend down slightly and swing the cape around him. The flames of his face tickle your hands slightly as you tie the strings into a fancy knot. Simple, yet elegant.  
  
“Ta-da!” You step back to admire your work. “Now for the rest of the night, you must speak in a Transylvanian accent!”

He blinks at you, bewildered. “A what?”

“Never mind. Come on Dracula, let’s get going!” You take his hand and pull him along. The haunted house isn’t far and fortunately is open late, given the day. There’s a fairly long line filled with a variety of monsters, humans, humans dressed as monsters and people who look like the last thing they want to be doing is going into a haunted house. This particular place is set up in an old abandoned zoo, which several different themed 'houses' set up. It's by far the most popular one in the city, known for it's realistic props and actors that just barely toe the line of the 'no touch' rule.

Grillby looks at the entryway, eyeing the dark aesthetics with something akin to hesitation. “So people go into these places to be scared…on purpose?”

You nod gleefully but not without a touch of nerves. “I’ve wanted to go to one for a while but I’ve been too chicken. So thanks for coming with me.”

He nods and then it’s your turn to go in. The bored lady at the ticket counter is snapped out of her stupor at the sight of a literal man on fire. Her jaw drops as her gaze shoots to you and back to Grillby and you feel a small surge of you might even call smugness at her wide expression.

“Um, that’ll be fifteen fifty,” she whispers and Grillby pays for both of your tickets before you can even grab your wallet. Beyond the ticket booth is a short walkway that leads to a pair of double doors manned by a guy in a butler outfit. His expression stays neutral as he opens the doors and gestures you inside. The rush of cool air makes Grillby’s flames sputter. 

The doors slam shut with a loud clang and you jump, pressing against Grillby’s arm. With the outside noise cut off, you can now hear the sound of whispering voices and a deep thudding that you rattles your bones and makes the hair on your skin rise.

Grillby looks around, his flames dimming slightly, perhaps in an attempt to maintain the atmospheric lighting. He follows as you release your grip on his arm and begin walking down the hall. A thin layer of fog hisses out from some hidden machine, making it a little hard to see where you’re going. This first area seems to be more of a classic haunted house set up; long twisting hallways with flickering electronic candles on the walls. Portraits hang on the wall, all of the people within painted with ghoulish features and eyes aglow that seem to follow you as you walk by. 

As you continue, the walls grow closer, twisting at sharp angles. The building dread is starting to become unbearable.

“Heh, just you wait,” you say to Grillby in an attempt to calm yourself. “There will be a jump scare at any moment!”

A sudden creak makes you grab onto him again, but you don’t see anything. The lights suddenly flicker and die but thanks to Grillby, you can still see well enough.

“That’s worrying,” you mutter.

A flash of movement out of the corner of your eyes makes your head whip around and you just barely catch a dark face staring at you from a hole in the wall that promptly vanishes.

Then, from the exact spot in the opposite wall, a section drops away and an actor backlit by a sickly green light and dressed in ghoulish make up lunges at the two of you, snarling loudly. You shriek and pull at Grillby as you break into a run.

The hallway turns a corner and you almost run into another actor holding what looks like his severed arm in his remaining hand as he slumps against the wall. Very realistic looking blood drips from the stump.

“Get out!” He moans, lurching towards you. “Leave while you still can!”

Screaming, you dodge him, and jump at the sound of something heavy slamming against the wall. But once you round another corner, you’re finally given a moment to breathe.

“Whoo!” Your heart is absolutely racing. You pad at your face with your sleeve. “Wow that was a lot all at once!”

Grillby doesn’t say anything. In fact…he’s been utterly silent ever since you walked in. You look up at him, eyes widening at the erratic sputtering of his fire and the honestly sickly hue they’ve taken on. “Are you okay?”

He simply nods but now you notice that under your hand, he’s stiff as a board.

And just like that, your own racing heart calms a little. You lick at your dry lips, glancing down the hallway. You have no doubts there are more spooks ahead but surely it’s not much longer, right? You release his arm and instead take his hand. He jumps just a little, tearing his gaze away from the direction you just came.

“Man, did you see that guy? Was he even trying?” You roll your eyes. “I thought this was supposed to be the scariest house around! I’m not even spooked a little, are you?”

Grillby takes in your shaky smile and sweaty hands and a flicker of a smile crosses his face. “Not at all.”

A low moan rises from behind you and you both jump, your hands tightening around each other. “B-but you know, maybe we should move on,” you squeak.

He nods quickly. “Good idea.”

The two of you move at a fairly fast pace through the rest of the haunted house. There are indeed several more spooks but now that you’ve got Grillby’s hand wrapped tightly around yours, you find yourself laughing more than screaming. He’s still fairly quiet, though you can feel it every time he jumps. And he never once loosens his grip on you. Continuing on leads you deeper into the zoo, passing through a maze with draping cobwebs that Grillby has to take extra care not to accidently set on fire, a butcher shop with a shrieking actor that chases you with a buzzing chainsaw and a house of clowns that has you pressing your face into Grillby's arm through most of it. It's when you pass through the house of dolls, with piles and piles of life sized dolls that hide the real people that very slowly turn their heads and scream that Grillby himself finally shrieks, a soft, breathless sort of sound that has you keeling over from laughter. 

The final area is a cemetery, with far too many hiding places for actors to pop out. Fog drifts around the tombstones, making it difficult to see the path out. But finally, finally! You see a dark doorway with a glimmer of light at the end. Grillby spots it too and takes the lead, pulling you forward when-

A hatch in the ceiling of the small hallway pops open and an upside down skeleton drops down right in front of Grillby, glowing slightly in the black light. He lets out a startled yell, jumping back with a flash of sparks and you crash into him.

The skeleton starts _moving_ , waving it’s arms. “boo or whatev-oh hey guys.”

The two of you stare at Sans, dressed in torn black reaper robes and hanging upside down for a moment before you laugh wildly. “ _Seriously_? You work _here_?”

Sans shrugs. “gotta do what you gotta do right? plus it’s fun to see gushy couples on dates scream like babies.”

Grillby taps Sans on the head. “For that, your tab is now due tomorrow.”

“aw c'mon grillbz!” Sans whines as Grillby pulls you around him and to the exit. You give Sans a wave as the fresh night air washes over your sweaty face. You release a breath, adrenaline making you shake a little.

“How many jobs does that guy have?” you ask Grillby.

“I’ve learned not to ask,” he mutters, rolling his golden eyes.

You laugh and then you become aware that you and Grillby are still holding hands. It’s nice. “Did you like it?” You gesture back to the house. “Now that it’s over I mean.”

"Do you want the honest answer or the nice one?" 

"Hmm, mixture of both?"

Grillby laughs, the sound like crackling logs. “Well, I certainly wouldn’t go back on my own,” he says dryly. But his gaze is soft as he looks at you. "But I suppose it wasn't so bad going with you." 

You grin bashfully. “Same to you.”

“Still, you humans have _really_ odd tastes in entertainment.”

“Says the guy who does nothing but work! Do you even know how to have fun?”

Grillby leans closer to you. Your heart, which had finally started to slow, races into overdrive again. “Believe me, I know how to have fun. I’ll have to show you sometime.”

You match his smirk. “I’m holding you to that, Mr. Bartender.”


End file.
